From 7ab87deaa91bd19527da2c72937b1e2d1a97ef12 Mon Sep 17 00:00:00 2001
From: Jakob Odersky <jakob@odersky.com>
Date: Tue, 11 Oct 2016 01:08:14 -0700
Subject: Initial commit

---
 src/main/scala/gh/Http.scala | 114 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 src/main/scala/gh/Http.scala

(limited to 'src/main/scala/gh/Http.scala')

diff --git a/src/main/scala/gh/Http.scala b/src/main/scala/gh/Http.scala
new file mode 100644
index 0000000..c72a24e
--- /dev/null
+++ b/src/main/scala/gh/Http.scala
@@ -0,0 +1,114 @@
+package gh
+
+import akka.NotUsed
+import akka.actor.ActorSystem
+import akka.http.scaladsl.model.{ MediaTypes, ResponseEntity }
+import akka.http.scaladsl.model.Uri.Query
+import akka.http.scaladsl.model.headers.Accept
+import akka.http.scaladsl.model.{ ContentType, RequestEntity, Uri }
+import akka.http.scaladsl.model.Uri.Path
+import akka.http.scaladsl.model.headers.{ Link, LinkValue }
+import akka.http.scaladsl.model.headers.LinkParams
+import akka.http.scaladsl.model.{ HttpRequest, HttpResponse, HttpHeader}
+import akka.http.scaladsl.unmarshalling.{ Unmarshal, Unmarshaller }
+import akka.http.scaladsl.unmarshalling.FromResponseUnmarshaller
+import akka.stream.{ BidiShape, Materializer }
+import akka.stream.scaladsl.{ BidiFlow, Broadcast, Flow, GraphDSL, Merge, Sink, Source }
+import akka.http.scaladsl.{HttpExt, Http}
+import scala.concurrent.ExecutionContext
+import spray.json.{ JsonParser, JsonReader }
+import spray.json.JsonReader
+
+trait HttpClient {
+
+  def client: HttpClient
+
+  trait HttpClient {
+    def get[A: JsonReader](path: String): Source[A, NotUsed]
+  }
+
+}
+
+trait AkkaHttpClient extends HttpClient {
+
+  class AkkaHttpClient(host: String)(implicit system: ActorSystem, materializer: Materializer) extends HttpClient {
+    
+    val http = Http(system)
+
+    def get[A: JsonReader](path: String): Source[A, NotUsed] = {
+      implicit val ec = materializer.executionContext
+
+      val uri = Uri() withScheme("https") withHost(host) withPath(Path(path))
+      val request = HttpRequest(uri = uri) withHeaders(Accept(MediaTypes.`application/json`))
+
+      println(request)
+      val um = implicitly[FromResponseUnmarshaller[String]].map(text => {
+        val v = JsonParser(text)
+        println(v.prettyPrint)
+        v.convertTo[A]
+      })
+
+      Source.single(request)
+        .via(paginate(100).join(http.outgoingConnectionHttps(host)))
+        .mapAsync(10)(um.apply)
+    }
+
+
+    def paginate(itemsPerPage: Int):
+        BidiFlow[HttpRequest, HttpRequest, HttpResponse, HttpResponse, NotUsed] = {
+      BidiFlow.fromGraph(GraphDSL.create() { implicit builder =>
+        import GraphDSL.Implicits._
+
+        val initialRequest = builder.add(Flow[HttpRequest].take(1))
+
+        // set number of items per page
+        val perPage = builder.add(Flow[HttpRequest].map{ req =>
+          val uri = req.uri withQuery Query("per_page" -> itemsPerPage.toString)
+          req withUri uri
+        })
+
+        // get next request from a paginated response
+        val nextPage = builder.add(Flow[HttpResponse].takeWhile{
+          case NextPage(_) => true
+          case _ => false
+        }.map{
+          case NextPage(next) => next
+        })
+
+        val merge = builder.add(Merge[HttpRequest](2))
+        val split = builder.add(Broadcast[HttpResponse](2))
+
+        initialRequest ~> perPage ~> merge
+        split.out(0) ~> nextPage ~> merge
+
+        BidiShape(initialRequest.in, merge.out, split.in, split.out(1))
+      })
+    }
+
+    def unmarshal[A](implicit u: Unmarshaller[ResponseEntity, A], ec: ExecutionContext): Flow[HttpResponse, A, NotUsed] = {
+      Flow[HttpResponse].mapAsync(10){ response =>
+        if (response.status.isSuccess()) {
+          Unmarshal(response.entity).to[A]
+        } else {
+          throw new RuntimeException("Unsuccessful response status code: " + response.status.value)
+        }
+      }
+    }
+
+    // Extractor for responses containing a 'Link' header to a next page, i.e.
+    // Link: <https://api.github.com/user/repos?page=3&per_page=100>; rel="next"
+    private object NextPage {
+      def unapply(response: HttpResponse): Option[(HttpRequest)] = {
+        val next = for (
+          Link(values) <- response.header[Link].toSeq;
+          LinkValue(nextUri, Seq(LinkParams.rel("next"))) <- values
+        ) yield {
+          HttpRequest(uri = nextUri)
+        }
+        next.headOption
+      }
+    }
+
+  }
+
+}
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